#include <bits/stdc++.h>
#include <unordered_set>

using namespace std;

ifstream fin("ciur.in");
ofstream fout("ciur.out");

int n;
unordered_set<int> notPrime;

int main() {

    fin >> n;

    for (int i = 2; i <= sqrt(n) ; i++) {
        if (notPrime.find(i) != notPrime.end()) {
            continue;
        }
        int j = i * 2;
        while (j <= n) {
            notPrime.insert(j);
            j += i;
        }
    }

    fout << n - notPrime.size() - 1;
    return 0;
}